Did our two Viking landers find life on Mars in 1976? Astonishingly, thirty seven years later, we still haven't sent anything to Mars able to answer this question for sure. None of our spacecraft since Viking would be able to spot life which we now know exists in the driest deserts on Earth, and only one of the experiments on Viking had this capability. There are hypotheses about what they found, but no definite proof.
A few years back, to everyone's complete surprise, Joseph Miller, specialist in rhythms of life, spotted smooth daily cycles in the data from 1976, strongly suggesting life processes. So did Viking spot life or are these smooth cycles signs of something else, perhaps some complex chemistry?